The invention concerns a method of precisely positioning a male die member on a backing roller of a stamping station, which backing roller co-operates with a stamping roller, wherein at its cylindrical peripheral surface the stamping roller has a die with a die relief structuring and the male die member which is provided with a male die member relief structuring negatively corresponding to the die relief structuring is positioned on the cylindrical peripheral surface of the backing roller in accurate fitting relationship with the die on the cylindrical peripheral surface of the stamping roller.
Such a known method involves using a male die member comprising a thin, flexible, that is to say bendable and curvable material, in order to be able to temporarily mount the male die member to the die provided on the cylindrical peripheral surface of the stamping roller. Then, during a simultaneous rotary movement of the stamping roller and the backing roller, the male die member which Is temporarily fixed to the die on the stamping roller is transferred from the stamping roller to the backing roller and fixed on the cylindrical peripheral surface of the backing roller. During that transfer the male die member is curved from the direction of curvature of the stamping roller into the oppositely directed direction of curvature of the backing roller, and for that reason the male die member therefore has to be suitably flexible, that is to say bendable or curvable.
The stamping station which is assembled in that way, with the die on the stamping roller and the male die member on the backing roller, is then available for carrying out relief stamping operations in order for example to structure paper with a relief and at the same time to apply a stamping foil thereto by a stamping or embossing operation. In order to carry out such a relief stamping operation however it is necessary that not only the die on the stamping roller but also the male die member on the backing roller are suitably hard and stable in relation to pressure. That requirement in terms of hardness and stability in respect of pressure is in conflict with the requirement for flexibility and workability of the male die member, this therefore resulting in corresponding limitations.
The object of the present invention is to provide a method of the kind set forth in the opening part of this specification, in which the contradiction between stability in respect of pressure and hardness of the male die member with the requirement for flexibility and curvability thereof is eliminated in a simple fashion.
In accordance with the invention in a method of the kind set forth in the opening part of this specification that object is attained in that a thin flexible bendable transfer male die member having a fitting window is temporarily fixed in accurately positioned relationship to the die of the stamping roller, that the transfer male die member is transferred from the stamping roller to the backing roller and fixed to the backing roller, wherein the stamping roller and the backing roller are driven in rotation in mutually opposite relationship at mutually corresponding peripheral speeds, and that then the male die member is fixed in accurate fitting relationship in the fitting window of the transfer male die member fixed to the backing roller, wherein the male die member provided with the male die member relief structuring comprises a thin material which is stable in respect of shape and which has a cylindrical curvature corresponding to the curvature of the cylindrical peripheral surface of the backing roller.
The method according to the invention involves using a thin, flexible, bendable transfer male die member and a male die member which is stable in respect of shape. The transfer male die member only serves to establish on the backing roller the position for the male die member which is stable in respect of shape, said position corresponding in accurately fitting relationship to the die of the stamping roller. The transfer male die member can therefore advantageously comprise a flexible, bendable material. The male die member which is prefabricated with the male die member relief structuring advantageously comprises a material which is stable in respect of shape. In accordance with the invention the above-mentioned conflict between flexibility and bendability or curvability and stability in respect of pressure and hardness of known male die members is advantageously eliminated.
The method according to the invention preferably uses a transfer male die member which has a synthetic resin layer on a woven base cloth, wherein the synthetic resin layer on the base cloth forms a frame which definedly delimits the fitting window for the male die member of material which is stable in respect of shape. It is preferred in that respect if the synthetic resin layer is of a thickness which corresponds to the thickness of the male die member. Such a configuration provides that the male die member with the relief structuring thereon and the synthetic resin layer forming a frame around the male die member blend into each other smoothly and continuously and without a step, which has a positive effect on the stamping properties of the stamping station.
The method according to the invention can use a transfer male die member, wherein the base cloth is a glass fiber cloth and the synthetic resin layer is an epoxy resin layer. Transfer male die members of that kind have an optimum service life.
It is advantageous if the transfer male die member is glued fast with its base cloth to the cylindrical peripheral surface of the backing roller. For that purpose the transfer male die member and/or the cylindrical peripheral surface of the backing roller can be provided with a suitable adhesive. Likewise it is desirable if the prefabricated male die member which involves a cylindrical curvature corresponding to the curvature of the cylindrical peripheral surface of the backing roller and which comprises material that is stable in respect of shape and for example involves brass or the like is glued fast in the fitting window of the transfer male die member.
The method according to the invention results in a stamping station for relief structuring and stamping of suitable sheet or web material such as paper or the like, wherein the stamping station, with an excellent service life, permits precise operation, that is to say structuring and stamping. Further details, features and advantages will be apparent from the description hereinafter of an embodiment of the method according to the invention and essential method steps thereof, which is shown in highly diagrammatic form in the drawing in which: